DDT降解菌株Chryseobacterium sp. PYR2对小麦的促生作用及其机理

【背景】前期结果表明,DDT降解菌株Chryseobacterium sp. PYR2可高效去除土壤中的DDT等污染物,具有潜在的应用价值,但该菌对植物的影响尚不清楚。【目的】探讨菌株Chryseobacterium sp. PYR2对植物的促生作用及其机理,为后续开发DDT降解及植物促生双效功能菌剂提供理论依据。【方法】配制该菌株的不同梯度稀释菌悬液,用纸卷发芽法和盆栽法研究菌悬液对小麦种子萌发和植株生长的影响;Salkowski法测定PYR2合成吲哚-3-乙酸(Indole-3-acetic acid,IAA)量;单因素实验研究不同培养条件对菌株生长及IAA合成的影响;液相色谱-串联质谱-多反应监测(LC-MS/MS-MRM)方法分析IAA在PYR2菌体内的生物合成途径。【结果】PYR2菌悬液可明显提高小麦种子萌发率并促进小麦植株的生长,小麦的侧根数、株高、鲜重、干重等指标均明显提高。该作用是由于菌株PYR2可以合成植物生长激素IAA。最适IAA合成条件:温度30°C,pH 7.0-8.0,盐浓度0.5%,L-色氨酸50mg/L。代谢液中检测到色醇、色胺和吲哚-3-乙酰胺3种中间代谢产物,推测PYR2体内存在3条IAA合成途径,分别为吲哚-3-丙酮酸(IPy A)、TAM和IAM途径。【结论】菌株PYR2对小麦具有明显的促生效果,是由于其具有多条高效合成IAA的代谢途径,表明其在农药污染土壤的生物修复及作物种植中具有潜在的应用前景。

Plant growth-promoting effect and its mechanism of the DDT-degrading strain PYR2

Background] Previous results showed that the DDT-degrading strain, Chryseobacterium sp. PYR2, could efficiently remove DDT and other pollutants from contaminated soil and was great potential in bioremediation. However, the influence of PYR2 on plants and also microorganism-plant interactions is not clear. Objective] In this study, the plant growth-promoting efficiency and its mechanism of strain PYR2 was investigated, thus providing the theoretical basis for the further development of DDT degradation and plant growth-promoting dual-effect bacterial agents. Methods] Seed soaking and plant pot experiments were conducted to reveal the plant growth promoting effects of PYR2 on wheat. Salkowski method was used to detect the concentration of indole-3-acetic acid (IAA). Single factor experiments were performed to detail the effects of different culture conditions on its growth and IAA yield. Liquid chromatography-tandem mass spectrometry-multiple reaction monitoring (LC-MS/MS-MRM) detection was employed to detect the intermediate metabolites of IAA biosynthetic process. Results] Seed germination rates of wheat was greatly enhanced, and so the growth of wheat plants by using cell suspension of PYR2, as the significant increase of height, lateral root number, fresh weight as well as dry weight. The optimum IAA synthesis conditions were temperature 30 °C, pH 7.0?8.0, salt ion concentration <0.5%, L-tryptophan 50 mg/L. The intermediate metabolites of IAA synthesis were tryptophol (TOL), tryptamine (TAM) and indole-3-acetamide (IAM), suggesting that there are three different IAA synthetic pathways in PYR2 (IPyA, TAM and IAM). Conclusion] Strain PYR2 exhibited significant plant growth promoting effects on wheat, due to its multiple and effective IAA biosynthetic pathways. These results suggest that PYR2 is greatly potential in the bioremediation of and plant-growth in pesticide contaminated soil.